Dipole antenna arrays

ABSTRACT

Dipole antenna arrays are disclosed. An example dipole antenna array includes a ground plane having a first serrated edge, and a first dipole antenna, at least a portion of the first dipole antenna disposed parallel to the first serrated edge.

RELATED APPLICATION

This application claims the priority from U.S. Provisional PatentApplication No. 62/490,984, entitled “Dipole Antenna Row with CorrugatedGround Plane,” and filed on Apr. 27, 2017, the entirety of which isincorporated herein by reference.

FIELD OF THE DISCLOSURE

This disclosure relates generally to antennas, and, more particularly,to dipole antenna arrays.

BACKGROUND

Measuring the angle of arrival (AoA) of an incoming radio frequency (RF)signal may be performed using a single antenna with high directivity, orusing an array of smaller antenna elements and measuring or altering theRF signal phase between the elements.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example RF radio in which an exampleground plane and an example dipole antenna, according to thisdisclosure, may be implemented.

FIG. 2 illustrates an example implementation of the example ground planeof FIG. 1.

FIG. 3 illustrates an example implementation of the example serratededge of FIG. 1 and/or FIG. 2.

FIG. 4 is a plan view of an example implementation of the example groundplane and example dipole antenna of FIG. 1.

FIG. 5 is a plan view of an example enlarged portion of the exampleground plane and example dipole antenna array of FIG. 4.

FIG. 6 is an image of an example implementation of an example printedcircuit board (PCB) shown in FIG. 1.

FIG. 7 is a plan view of an example implementation of the example groundplane of FIG. 6.

FIG. 8 is an oblique view of a portion of the example ground plane andexample dipole antenna array of FIG. 6 and/or FIG. 7.

FIG. 9 illustrates another example implementation of the example groundplane and example dipole antenna of FIG. 1.

FIG. 10 illustrates example processes that may be carried out to formthe example RF radios and PCBs disclosed herein.

The figures are not to scale. Instead, to clarify multiple layers andregions, the thickness of the layers may be enlarged in the drawings.Wherever possible, the same reference numbers will be used throughoutthe drawing(s) and accompanying written description to refer to the sameor like parts. Connecting lines or connectors shown in the variousfigures presented are intended to represent example functionalrelationships and/or physical or logical couplings between the variouselements. As used in this patent, stating that any part (e.g., a layer,film, area, or plate) is in any way positioned on (e.g., positioned on,located on, disposed on, or formed on, etc.) another part, indicatesthat the referenced part is either in contact with the other part, orthat the referenced part is above the other part with one or moreintermediate part(s) located therebetween. Stating that any part is incontact with another part means that there is no intermediate partbetween the two parts.

DETAILED DESCRIPTION

An advantage of antenna arrays is that the antenna array can be madesmaller and cheaper than a conventional directive antenna, and digitalpost processing can be used to improve performance. Preferably, in anantenna array, the individual antenna elements only receive the directincoming RF signal, and do not receive reflections from neighboringantenna elements or a ground plane. In an antenna array, other antennaelements may be present, and an RF transceiver normally needs a groundplane, thus, preventing the spurious reflections from other antennaelements and the ground plane is difficult. In practice, the distancebetween antenna elements is fixed, requiring that the phase center ofthe elements be stable and independent of the direction of the RFsignal.

Example dipole antenna arrays that overcome at least these problems aredisclosed herein. In some disclosed examples, a differential (e.g.,dipole) antenna designed for use without the presence of a ground planeis used with a ground plane having a serrated edge. Disclosed exampleserrated edges reduce ground plane reflections that would otherwise haveimpaired antenna performance. Additionally, and/or alternatively, insome examples, the different antennas are placed in each other'szero-radiation direction (e.g., in a colinear or end-to-end arrangement)to reduce antenna-to-antenna coupling. By obviating, or at leastreducing, ground plane and antenna-to-antenna reflections, disclosedexamples implement stable phase centers regardless of an RF signal'sdirection of travel (a.k.a. AoA), and enable the phase difference(s)between the RF signal received at the different antennas in the array tobe used to determine AoA.

Reference will now be made in detail to non-limiting examples of thisdisclosure, examples of which are illustrated in the accompanyingdrawings. The examples are described below by referring to the drawings.

FIG. 1 is a block diagram of an example RF radio 100 including anexample ground plane 102 having an example serrated edge 104, and anexample dipole antenna array 106 disposed along the example serratededge 104. In the illustrated example of FIG. 1, the ground plane 102,the serrated edge 104, and the dipole antenna array 106 are disposed inan example PCB 108. While the examples disclosed are described inconnection with PCB-based antennas, antennas and ground planes havingserrated edges can be implemented at other scales (e.g., within anintegrated circuit, etc.). In some examples, the example PCB 108 of FIG.1 includes one or more layers, in addition to the example ground plane102, having traces, vias, etc. to carry signals, power, etc. In someexamples, the example ground plane 102 is a flat, thin, planar layer,foil or sheet of conductive material. An example ground plane 102 is10-50 micrometers (um) thick.

To generate and/or receive RF signals, the example RF radio 100 includesany type(s) and/or number(s) of example wireless transceivers, one ofwhich is designated at reference numeral 110. The example transceiver110 of FIG. 1 is communicatively coupled to the antenna 106 via one ormore traces 112 of the PCB 108. In some examples, a single transceiver110 is implemented that sequentially communicates with multipleantennas, for example, an example antenna 106A and an example antenna106B of the antenna array 106. In the illustrated example, thetransceiver 110 is coupled to the antennas 106A and 106B via respectivebaluns 107A and 107B and a switching matrix 113. In the illustratedexample of FIG. 1, the receiver chain between the antennas 106A and 106Band the transceiver 110 is the same for the antenna 106A and 106B so theonly change being measured is the move/switch from one antenna 106A,106B to the next antenna 106B, 106A. In some examples, phase shifters,power combiners, etc. are used in lieu of a switching matrix. Exampletransceivers 110 include, but are not limited to, a BLUETOOTH®transceiver, an Institute of Electrical and Electronics Engineers (IEEE)802.11x transceiver, a near field communication (NFC) transceiver, acellular communication system, a satellite communication system, etc. Insome examples, the transceiver 110 includes an RF module, modulators,de-modulators, mixers, amplifiers, filters, etc.

To transmit and/or receive data over the example transceiver 110 and theexample antenna array 106, the example RF radio 100 includes any numberand/or type(s) of processors, one of which is designated at referencenumeral 114. The example processor 114 of FIG. 1 is communicativelycoupled to the example transceiver 110 via one or more traces 116 of theexample PCB 108. In some examples, the processor 114 and the transceiver110 are implemented on the same integrated circuit die, e.g., in amonolithic system-on-a-chip (SoC) or wireless microcontroller unit(MCU). The example processor 114 may be implemented by, for example, aprogrammable processor, a programmable controller, a microprocessor, amicrocontroller, a graphics processing unit (GPU), a digital signalprocessor (DSP), an application specific integrated circuit (ASIC), aprogrammable logic device (PLD), a field programmable gate array (FPGA),a field programmable logic device (FPLD), etc.

The example RF radio 100 may implement, and/or be a part of a computingdevice such as, but not limited to, a computer, a mobile device (e.g., acell phone, a smart phone, a tablet such as an iPad), a personal digitalassistant (PDA), an Internet appliance, an Internet-of-Things (IoT)device, a headset, glasses, or other wearable device, a digitalversatile disk (DVD) player, a compact disc (CD) player, a digital videorecorder, a Blu-ray player, a gaming console, a personal video recorder,a set top box, or any other type of computing device.

While an example RF radio 100 is illustrated in FIG. 1, one or more ofthe elements and/or devices illustrated in FIG. 1 may be combined,divided, re-arranged, omitted, eliminated and/or implemented in anyother way. Further, the example RF radio 100 of FIG. 1 may include oneor more elements and/or devices in addition to, or instead of, thoseillustrated in FIG. 1, and/or may include more than one of any or allthe illustrated elements and devices.

The example serrated edge 104 of FIG. 1 may have any number of membersarranged in any number of pattern(s). Example patterns include aplurality of spaced-apart members in a serrated, toothed, comb-like,notched, fingered, etc. arrangement. In an illustrated top view examplein FIG. 2, the ground plane 102 includes a plurality of parallel,spaced-apart rectangular members 202 (e.g., fingers, fins, etc.)extending from a solid, base portion 204 of the ground plane 102. Whilerectangular members 202 are shown, other shapes and/or patters may beused. For example, meandered traces may be used to reduce the depth ofthe serrated edge 104. Referring to FIG. 3, an example end viewimplementation of the example serrated edge 104 includes the exampleground plane 102 adjacent (e.g., on, etc.) to another layer 302 of thePCB 108 (e.g., a substrate). The members 202 of the ground plane 102 andthe layer 302 form a corrugated (e.g., rippled, undulating, etc.)surface 304 having troughs 306 (e.g., valleys, etc.) and ridges 308(e.g., furrows, etc.).

FIG. 4 illustrates an example implementation of the example ground plane102, serrated edge 104, and antenna array 106 of FIG. 1. In theillustrated example of FIG. 4, the example antenna array 106 is acolinear dipole antenna array of example dipole antennas 402, 403 and404, although other numbers of antennas may be implemented. Any type ofdipole antenna may be used to implement the example dipole antennas402-404 of FIG. 4. In some examples, the antenna array 106 may be an RFdipole antenna array, and the individual dipole antennas may be RFdipole antennas. Each of the example dipole antennas 402-404 includestwo portions. For example, the dipole antenna 403 includes two portions406 and 408. The dipole antennas 402-404 may radiate in patterns that donot overlap in the immediate near-field. An example wave front isdesignated at reference numeral 410. As shown, the dipole antennas402-404 do not radiate in the direction of the other dipole antennas402-404. In the illustrated example, the traces used to implement thesub-elements of the antennas 402-404 are 0.4 mm wide, and are separatedby 0.8 mm when they split, and are 0.2× to 0.5× in length. In general,these dimensions depend on antenna design considerations such asimpedance, bandwidth, etc.

Advantageously, the phase center of a dipole antenna is at the feedingpoint of the dipole antenna, one of which is designated at referencenumeral 412, in the middle of the dipole antenna. However, dipoleantennas are fully differential and may need to be fed with a balancedsignal spaced apart from ground planes. A dipole antenna radiates byconducting current along the length of the dipole antenna. The current,if brought near a ground plane, induces a current, through the magneticfield of the dipole antenna, that travels the opposite direction of thecurrent in the antenna, effectively short circuiting the antenna.Unfortunately, separating the antenna from ground planes causes thereflection of received and transmitted RF signals by the ground planesto interfere with the antenna.

To overcome at least these problems, while retaining the benefits ofdipole antennas (e.g., stable phase centers), the example ground plane102 includes the example serrated edge 104, which may also be viewed asthe example corrugated surface 304. The example serrated edge 104includes the plurality of parallel, spaced-apart members 202. Examplegaps, one of which is designated at reference numeral 414, between themembers 202 are a quarter of a wavelength (of the signal beingtransmitted by the dipole antenna array 402-404) long. As shown in FIG.5, in a magnified portion of the illustrated example of FIG. 4, when thedipole antennas 402-404 are brought close to the serrated edge 104 ofthe ground plane 102, the current 502 induced in the ground plane 102 bythe current 504 in the antenna 402-404 is forced to travel a halfwavelength detour for each gap 414. The half wavelength detour causesthe polarity of the current 502 when it exits a gap 414 to be oppositethe polarity of the current when it entered the gap 414, thus,cancelling each other and not inducing a current in the ground plane102. Accordingly, the dipole antenna array 106 can be brought in verynear contact (e.g., 0 to 0.01×) to the ground plane 102 withoutcompromising antenna performance. Accordingly, the example serrated edge104 disclosed herein, which may also be viewed as the example corrugatedsurface 304, can be brought into very near contact with the ground plane102 to obviate out-of-phase RF reflections while preventing the groundplane 102 from short circuiting the dipole antennas 402-404. Exampledimensions of the example features of the example ground plane 102 ofFIG. 4 and FIG. 5 for RF signals for a 2.4 GHz carrier frequency areshown in FIG. 5, where X is the wavelength of the carrier frequency. Ingeneral, the width of the members 202 is chosen to break up currentsclose to the antenna array 106 while not being too small for practicaland/or cost-effective lithography. For example, a width of the members202 of approximately 0.01×, and a pitch of the members 202 of twice thewidth.

While an example ground plane 102 is illustrated in FIGS. 4 and 5, oneor more of the elements and/or devices illustrated in FIGS. 4 and 5 maybe combined, divided, re-arranged, omitted, eliminated and/orimplemented in any other way. Further, the example ground plane 102 ofFIGS. 4 and 5 may include one or more elements and/or devices inaddition to, or instead of, those illustrated in FIGS. 4 and 5, and/ormay include more than one of any or all the illustrated elements anddevices.

FIG. 6 is an example implementation of the example ground plane 102 ofFIG. 1. FIG. 7 is an oblique view of a portion of the example groundplane 102 and the example dipole antenna 403 of FIG. 6. In theillustrated example of FIG. 6, the example transceiver 110 (see FIG. 1)is electrically coupled to the example dipole antennas 402 via, forexample, the trace 112, the switching matrix 113 (not shown), and anexample balun 604 (e.g., a Marchand balun), and an example feedingnetwork 602. An example Marchand balun uses broad side coupledtransmission lines (meaning the transmission lines are implemented indifferent layers of a PCB). A Marchand balun is half of a wave length inlength, thus, it has been folded lengthwise and fits within the serratededge 104.

As seen best in FIG. 7, the example balun 604 and the example feedingnetwork 602 are shielded with an example top shield 702 and an examplebottom shield 704. The example top shield 702 and the example bottomshield 704 prevent the balun 604 and feeding network 602 frominterfering with other components of the PCB 108 or RF radio 100, and/orbeing interfered with by other components of the PCB 108 or RF radio100.

FIG. 8 is an image of an example implementation of the example PCB 108of FIG. 1 that includes the examples elements of FIGS. 6 and 7. As shownin the illustrated example of FIG. 8, the ground plane 102, the serratededge 104, the dipole antennas 402-404 are implemented as part of the PCB108, the shields 702 and 704. For example, the ground plane 102, theserrated edge 104 and the dipole antennas 402-404 are implemented withinthe PCB 108.

While an example PCB 108 is illustrated in FIGS. 6-8, one or more of theelements and/or devices illustrated in FIGS. 6-8 may be combined,divided, re-arranged, omitted, eliminated and/or implemented in anyother way. Further, the example PCB 108 of FIGS. 6-8 may include one ormore elements and/or devices in addition to, or instead of, thoseillustrated in FIGS. 6-8, and/or may include more than one of any or allthe illustrated elements and devices.

To widen the sector in which AoA measurements can be made, anarrangement of two or more of the example serrated edges 104, and two ormore of the example dipole antenna arrays 106 disclosed herein can beimplemented. In an illustrated example antenna arrangement 902 shown inFIG. 9, two example pairs 902 and 904 of serrated edges 104 and dipoleantenna arrays 106 are implemented. Because the example pairs 902 and904 of the illustrated example intersect at a relative angle ofapproximately 90 degrees, members 202 of the pair 902 are parallel with,and physically close to, but not collinear with, the half-wave dipoleantenna 906 of the other pair 904, and vice versa. Accordingly, fingers908 of the pair 902 closest to the corner 910 of the antenna arrangementof FIG. 9, and the half-wave dipole antenna 906 interfere with eachother, as illustrated with example wave fronts 912, and vice versa. Theinterference is exacerbated because the serrated edges 104 will resonateat the frequency in use, and the energy is not dissipated in the groundplane 102. Therefore, most of this RF energy will be re-radiated,causing problems for the nearest parallel dipole antenna.

To overcome at least these problems, a series resistor 914 (e.g., 200Ohms) is placed in the member 916 of each pair 902, 904 that is closestto the corner 910, and making a cut 918 (e.g., a non-conductive gap orportion) in each of the next two members 920 and 922 of each pair 902,904 to change their length to prevent the members 920, 922 fromresonating at the frequency in use. As a result, less RF energy will becoupled into the members 920 and 922 closest to the corner 910, and mostof the RF energy that is captured will be dissipated in the resistor914.

While an example antenna arrangement 900 is illustrated in FIG. 9, oneor more of the elements and/or devices illustrated in FIG. 9 may becombined, divided, re-arranged, omitted, eliminated and/or implementedin any other way. Further, the example antenna arrangement 900 of FIG. 9may include one or more elements and/or devices in addition to, orinstead of, those illustrated in FIG. 9, and/or may include more thanone of any or all the illustrated elements and devices.

A flowchart representative of example processes for forming, among otherthings, the example RF radio and PCBs disclosed herein is shown in FIG.10. Although the example processes of FIG. 10 are described withreference to the flowchart illustrated in FIG. 10, many other methods offorming the example RF radios and PCBs disclosed herein mayalternatively be used. For example, the order of execution of the blocksmay be changed, and/or some of the blocks described may be changed,eliminated, or combined.

The example processes of FIG. 10 begin with forming a bottom PCBsubstrate (block 1002) and forming a first ground plane on the substrate(block 1004). A serrated pattern is formed on one or more edges of thefirst ground plane to form one or more serrated edges (e.g., the exampleserrated edge 104) (block 1006). In some examples, the bottom substrateis the bottom most layer of the PCB. In some examples, the bottomsubstrate is formed on another layer of the PCB. In some examples, theserrated pattern is formed by removing portions of the first groundplane. Additionally, and/or alternatively, the first ground plane isformed according to the desired serrated pattern using, for example, thesame single etch and/or deposit process may be used to form first groundplane, and the serrated pattern. A second PCB substrate is formed on thefirst ground plane (1008). One or more inner layers are formed on thesecond PCB substrate (block 1010). The one or more inner layers includeone or more antennas 402-404 along one or more serrated edges of thefirst ground plane (e.g., see FIG. 6) or along one or more serratededges of a second ground plane discussed below, baluns (e.g., theMarchand balun 604), feeding networks (e.g., the example feeding network602), switching network(s), and traces (e.g., the example trace 112. Insome examples, the antennas, baluns, feeding networks and switchingnetworks are formed using, for example, a single etch and/or depositprocess. A third PCB substrate is formed on the inner layer(s) (block1012), and a second ground plane is formed on the third PCB substrate(block 1014). One or more serrated patterns are formed on one or moreedges of the second ground plane to form one or more serrated edges(e.g., the example serrated edge 104). In some examples, the serratedpatterns are formed by removing portions of the second ground plane.Additionally, and/or alternatively, the second ground plane is formedaccording to the desired serrated pattern using, for example, the sameetch and/or deposit process may be used to form the second ground plane,including the serrated pattern. In some examples, the second groundplane is not included. In some examples, additional traces are formed(e.g., the example trace 112) (block 1016), and a transceiver (e.g., thetransceiver 110) is mounted to the PCB, becoming coupled to theswitching network(s) (1018). The PCB may include additional, and/oralternative, layers or planes. In some examples, such as a single layerPCB, fewer layers are implemented. In an example single layer PCB, theconductor patterns of the PCB are formed in a single step. That is,antenna(s), ground plane(s), serrated edge(s), balun (s), matchingcircuit(s), switching network(s), RF trace(s), etc. are formed in thesame etch and/or deposit process. Control then exits from the exampleprocesses of FIG. 10.

Example dipole antenna arrays are disclosed herein. Further examples andcombinations thereof include at least the following.

Example 1 is a dipole antenna apparatus that includes a ground planehaving a first serrated edge, and a first dipole antenna, at least aportion of the first dipole antenna disposed parallel to the firstserrated edge.

Example 2 is the dipole antenna apparatus of example 1, furtherincluding a second dipole antenna positioned with the first dipoleantenna to form a colinear dipole antenna array disposed parallel to thefirst serrated edge.

Example 3 is the dipole antenna apparatus of example 2, wherein thefirst dipole antenna and the second dipole antenna radiate in the samedirection.

Example 4 is the dipole antenna apparatus of example 1, wherein thefirst dipole antenna and the ground plane are structured to be phasecenter stable.

Example 5 is the dipole antenna apparatus of example 1, wherein thefirst serrated edge includes two members, the two members beingapproximately a quarter wavelength of the first radio frequency (RF)signal in length.

Example 6 is the dipole antenna apparatus of example 5, wherein the twomembers are approximately 0.001 to 0.1 times the wavelength of the firstRF signal in width, and separated by approximately 0.001 to 0.1 timesthe wavelength of the first RF signal.

Example 7 is the dipole antenna apparatus of example 1, wherein thefirst serrated edge includes a plurality of spaced-apart parallelmembers extending from a solid portion of the ground plane.

Example 8 is the dipole antenna apparatus of example 7, furtherincluding: a second serrated edge of the ground plane, the secondserrated edge disposed at an angle relative to the first serrated end,the second serrated edge including a second plurality of spaced-apartparallel members extending from the solid portion of the ground plane;and a second dipole antenna disposed parallel to the second serratededge.

Example 9 is the dipole antenna apparatus of example 8, wherein a firstmember of the second plurality of spaced-apart parallel members includesresistor, and second and third members of the second plurality ofspaced-apart parallel members have non-conductive gaps.

Example 10 is the dipole antenna apparatus of example 9, wherein thefirst member is the closest one of the second plurality of spaced-apartparallel members to the first dipole antenna, and the second and thirdmembers are the next closest ones of the second plurality ofspaced-apart parallel members to the first dipole antenna.

Example 11 is the dipole antenna apparatus of example 7, wherein alength of a first of the plurality of spaced-apart parallel members isapproximately a quarter wavelength of the first RF signal.

Example 12 is the dipole antenna apparatus of example 7, wherein a firstof the plurality of spaced-apart parallel members has a rectangularshape.

Example 13 is the dipole antenna apparatus of example 1, wherein thefirst serrated edge is structured to reduce a boundary current in theground plane.

Example 14 is the dipole antenna apparatus of example 1, wherein thefirst dipole antenna is a first radio frequency (RF) dipole antenna.

Example 15 is the dipole antenna apparatus of example 1, furtherincluding a balun coupled to the first dipole antenna, a first groundshield positioned above the balun, and a second ground shield positionedbelow the balun.

Example 16 is the dipole antenna apparatus of example 1, furtherincluding a second dipole antenna, a switching network coupled to thefirst and second dipole antennas, and a transceiver alternativelycoupled to the first dipole antenna and the second dipole antenna viathe switching network.

Example 17 is a dipole antenna assembly including

a printed circuit board (PCB), the PCB including ground plane having aserrated edge, the serrated edge including a plurality of spaced-apartparallel members extending from a solid portion of the ground plane, acolinear dipole antenna array having a portion thereof disposed parallelto the serrated edge, baluns coupled to respective ones of elements ofthe colinear dipole antenna, and a switching network coupled to theelements of the colinear dipole antenna via respective ones of thebaluns;

a transceiver mounted to the PCB, the transceiver selectively coupled tothe elements of the colinear dipole antenna via the switching network;and

a processor mounted to the PCB, the processor communicatively coupled tothe transceiver.

It is noted that this patent claims priority from U.S. ProvisionalPatent Application Ser. No. 62/490,984, which was filed on Apr. 27,2017, and is hereby incorporated by reference in its entirety.

“Including” and “comprising” (and all forms and tenses thereof) are usedherein to be open ended terms. Thus, whenever a claim lists anythingfollowing any form of “include” or “comprise” (e.g., comprises,includes, comprising, including, having, etc.), it is to be understoodthat additional elements, terms, etc. may be present without fallingoutside the scope of the corresponding claim. As used herein, when thephrase “at least” is used as the transition term in a preamble of aclaim, it is open-ended in the same manner as the term “comprising” and“including” are open ended. Conjunctions such as “and,” “or,” and“and/or” are inclusive unless the context clearly dictates otherwise.For example, “A and/or B” includes A alone, B alone, and A with B. Inthis specification and the appended claims, the singular forms “a,” “an”and “the” do not exclude the plural reference unless the context clearlydictates otherwise.

Any references, including publications, patent applications, andpatents, cited herein are hereby incorporated by reference to the sameextent as if each reference were individually and specifically indicatedto be incorporated by reference and were set forth in its entiretyherein.

Although certain example methods, apparatus and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all methods,apparatus and articles of manufacture fairly falling within the scope ofthe claims of this patent.

What is claimed is:
 1. An apparatus, comprising: a ground plane having afirst serrated edge and a second serrated edge, the second serrated edgedisposed at an angle relative to the first serrated edge; a first dipoleantenna having a portion disposed parallel to the first serrated edge;and a second dipole antenna having a portion disposed parallel to thesecond serrated edge.
 2. The apparatus of claim 1, wherein the seconddipole antenna positioned with the first dipole antenna to form acolinear dipole antenna array disposed parallel to the first serratededge.
 3. The apparatus of claim 2, wherein the first dipole antenna andthe second dipole antenna radiate in the same direction.
 4. Theapparatus of claim 1, wherein the first dipole antenna and the groundplane are structured to be phase center stable.
 5. The apparatus ofclaim 1, wherein the first serrated edge includes two members, the twomembers being approximately a quarter wavelength of the first radiofrequency (RF) signal in length.
 6. The apparatus of claim 5, whereinthe two members are approximately 0.001 to 0.1 times the wavelength ofthe first RF signal in width, and separated by approximately 0.001 to0.1 times the wavelength of the first RF signal.
 7. The apparatus ofclaim 1, wherein the first serrated edge includes a plurality ofspaced-apart parallel members extending from a solid portion of theground plane.
 8. The apparatus of claim 7, wherein the second serratededge including a second plurality of spaced-apart parallel membersextending from the solid portion of the ground plane.
 9. The apparatusof claim 8, wherein a first member of the second plurality ofspaced-apart parallel members includes resistor, and second and thirdmembers of the second plurality of spaced-apart parallel members havenon-conductive gaps.
 10. The apparatus of claim 9, wherein the firstmember is the closest one of the second plurality of spaced-apartparallel members to the first dipole antenna, and the second and thirdmembers are the next closest ones of the second plurality ofspaced-apart parallel members to the first dipole antenna.
 11. Theapparatus of claim 7, wherein a length of a first of the plurality ofspaced-apart parallel members is approximately a quarter wavelength ofthe first RF signal.
 12. The apparatus of claim 7, wherein a first ofthe plurality of spaced-apart parallel members has a rectangular shape.13. The apparatus of claim 1, wherein the first serrated edge isstructured to reduce a boundary current in the ground plane.
 14. Theapparatus of claim 1, wherein the first dipole antenna is a first radiofrequency (RF) dipole antenna.
 15. The apparatus of claim 1, furtherincluding: a balun coupled to the first dipole antenna; a first groundshield positioned above the balun; and a second ground shield positionedbelow the balun.
 16. The apparatus of claim 1, further including: aswitching network coupled to the first and second dipole antennas; and atransceiver alternatively coupled to the first dipole antenna and thesecond dipole antenna via the switching network.
 17. An assembly,comprising: a printed circuit board (PCB), including: a ground planehaving a serrated edge and a second serrated edge, the second serratededge disposed at an angle relative to the first serrated edge; a firstdipole antenna having a portion disposed parallel to the first serratededge; and a second dipole antenna having a portion disposed parallel tothe second serrated edge.